The present invention relates to an incineration system and especially to an incinerator for solid refuse.
As municipal land waste areas continue to become completely filled, alternate methods of refuse disposal assume an increasingly large importance. This problem results in efforts to totally destroy the refuse, especially through burning. This undertaking must comply with current environmental restrictions but burning the material and recovering the heat energy produced is an especially tantalizing goal in an age of high energy cost.
The main combustion chambers that the entering refuse initially encounter have also witnessed a wise degree in variation of designs. Some incinerators place the refuse upon a grate bed. This allows the air or other oxygen-containing gas to readily and uniformly intermingle with the refuse to assure complete combustion. However, unburned ash, plastics, wet refuse, and liquids may simply drop down through the grates to the bottom of the incinerator. There they undergo combustion and can provide excessive heat to the incinerator's lower surface and grating structure, possibly damaging them. A hearth, or refractory, floor represents an alternative to the grate support for refuse.
Initially, the refuse upon the floor must receive an even distribution of oxygen in order for the bulk of the material to burn. This throughput of oxygen does not occur if the air simply passes into the combustion chamber over the burning refuse; it must enter underneath the waste material and disperse throughout. The uniform dispersion of the air into the waste requires the placement of air nozzles within the hearth floor itself. However, the heavy refuse sitting upon the floor has shown an unmistakable propensity to clog and destroy the effectiveness of the air-introducing nozzles. As a result, the refuse does not undergo efficient and thorough combustion.
To prevent the clogging of nozzles in a hearth floor, some incinerators force the air through at a high velocity. However, the fast-moving gases display a tendancy to entrain particles and produce smoke. Furthermore, the high velocities have a tendency to create a "blow torch" effect and produce slag. The slag may then stick to the hearth floor and interfere with the chamber's subsequent operation.
Incinerators currently in use employ drastically different geometric designs for the initial combustion chamber. For example, some use a tall compartment occupying a relatively small horizontal area. Others utilize cylindrical chambers with the main axis of cylindrical symmetry lying horizontally. Most also use chambers with a minimal volume to permit the burning of the intended refuse. All of these factors increase the velocity of gases passing through and thus the entrainment of particulate, smoke-producing material.
The incinerators of the days before environmental concern simply released their exhaust gases from the combustion chamber into the atmosphere. The detrimental effect of these gases upon the environment has resulted in prohibitions of their continued use. Moreover, it has led to the development of additional techniques for controlling the pollutants produced in the combustion chamber.
Efforts to control pollution have often centered upon the use of a reburn tunnel to effectuate further combustion of the main combustion chamber's exhaust. The gases, upon departing the main combustion chamber, immediately enter the reburn unit. The tunnel may include a burner to produce heat and a source of oxygen, usually air, to complete the combustion process. The additional oxygen, of course, represents an essential ingredient for the starved-air incinerators. Depending upon the material introduced in the main chamber, the reburn unit provides a set amount of fuel to the burner and a specified amount of oxygen.
Furthermore, many incinerators, while attempting to avoid degrading the environment, have also sought to recover the heat produced by the combustion. Some try to capture heat directly within the main combustion chamber. Others choose to locate a boiler adjacent the reburn unit, maximizing the recovery of the produced energy while avoiding substantial pollution.
Prior U.S. patents having incinerator systems can be seen in the Spitz et al. U.S. Pat. No. 4,183,307 for a pollution control incinerator system having a series of connected combustion stations each one connected in series to the other with a branch duct. The Schregg U.S. Pat. No. 3,785,305 teaches an incinerator where the refuse is fed into a main combustion chamber by a compactor through a chute and the gases are fed to an afterburner air feed system. The Beausoleil et al. U.S. Pat. No. 4,850,289 teaches an incinerator having a loading member with a burning chamber and a combustion chamber along with a duct member connecting the burning and the combustion chambers. The Basic Sr. U.S. Pat. No. 4,438,705 teaches an incinerator with two reburn stages and optional heat recovery. The Normantas U.S. Pat. No. 4,029,026 teaches an incinerator which eliminates the independently fired afterburner. The LePori et al. U.S. Pat. No. 4,848,249 teaches a system for conversion of trash to usable energy in which the trash is fed into a primary burner while the exhaust is fed through a series of vortexes to remove ash and the like and the exhaust is then fed to an afterburner. The burning is from the bottom of the principal combustion chamber.
The present invention relates to a multistage incinerator having an elongated hearth having a plurality of plenum ducts feeding from different portions thereof and having a burner car mounted on a track on an open side of the hearth for passing the burner and a refuse agitating system from one zone to another zone along the hearth. The hearth can be continuously refilled as the burner car moves from one zone to the other across the length of the hearth. Each of the plenums is powered by an independent fan feeding a cyclone ash remover and an afterburner.